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<p>The Xenarthra superorder includes two key anteater species in Brazil, <i>Myrmecophaga tridactyla</i> and <i>Tamandua tetradactyla</i>, which play crucial ecological roles but are threatened by habitat loss and anthropogenic impacts. This study provides a comprehensive quantitative assessment of cardiac morphology in these species, measuring 25 variables related to mass, volume, linear axes, and wall thickness in 61 hearts: 48 from <i>M. tridactyla</i> (23 males, 20 females, 5 undetermined) and 13 from <i>T. tetradactyla</i> (7 males, 6 females). After normalization by the main cardiac vertical axis, univariate analyses revealed limited sex-related differences, restricted to a few size-associated indices in <i>T. tetradactyla</i>. The MANOVA revealed a highly significant multivariate difference between the species (Wilks’ λ = 0.2671; <i>p</i> &lt; 0.001). PCA based on 24 standardized indices further indicated directional multivariate differences between species, with <i>M. tridactyla</i> tending toward proportionally larger and wider cardiac configurations, whereas <i>T. tetradactyla</i> occupied comparatively more compact regions of the morphospace. A second PCA indicated only subtle sexual variation within <i>T. tetradactyla</i>. In contrast, the PCA for <i>M. tridactyla</i> revealed a marked ontogenetic shift, with juveniles forming a non-overlapping cluster relative to adults along the primary size-related component, reflecting systematic proportional remodeling during postnatal growth. These findings indicate that interspecific differences in cardiac design are aligned with body size and ecological demands, whereas sexual dimorphism plays only a minor role. This study establishes the first detailed multivariate framework for anteater cardiac morphology, offering reference parameters relevant for comparative anatomy, veterinary practice, and conservation biology.</p>

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Heart of anteaters: a morphometric portrait of two myrmecophagid species

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月24日

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  • Wilson Viotto-Souza,
  • André Luiz Quagliatto Santos,
  • Paulo de Souza-Junior

摘要

The Xenarthra superorder includes two key anteater species in Brazil, Myrmecophaga tridactyla and Tamandua tetradactyla, which play crucial ecological roles but are threatened by habitat loss and anthropogenic impacts. This study provides a comprehensive quantitative assessment of cardiac morphology in these species, measuring 25 variables related to mass, volume, linear axes, and wall thickness in 61 hearts: 48 from M. tridactyla (23 males, 20 females, 5 undetermined) and 13 from T. tetradactyla (7 males, 6 females). After normalization by the main cardiac vertical axis, univariate analyses revealed limited sex-related differences, restricted to a few size-associated indices in T. tetradactyla. The MANOVA revealed a highly significant multivariate difference between the species (Wilks’ λ = 0.2671; p < 0.001). PCA based on 24 standardized indices further indicated directional multivariate differences between species, with M. tridactyla tending toward proportionally larger and wider cardiac configurations, whereas T. tetradactyla occupied comparatively more compact regions of the morphospace. A second PCA indicated only subtle sexual variation within T. tetradactyla. In contrast, the PCA for M. tridactyla revealed a marked ontogenetic shift, with juveniles forming a non-overlapping cluster relative to adults along the primary size-related component, reflecting systematic proportional remodeling during postnatal growth. These findings indicate that interspecific differences in cardiac design are aligned with body size and ecological demands, whereas sexual dimorphism plays only a minor role. This study establishes the first detailed multivariate framework for anteater cardiac morphology, offering reference parameters relevant for comparative anatomy, veterinary practice, and conservation biology.